Non-flamable elastomeric fiber from a fluorinated elastomer and containing an halogenated flame retardant

ABSTRACT

Flame retardant elastomeric compositions comprised of either spandex type polyurethane having incorporated into the polymer chain halogen containing polyols, conventional spandex type polyurethanes in physical admixture with flame retardant additives or fluoroelastomeric resins in physical admixture with flame retardant additives, methods of preparing fibers of the flame retardant elastomeric materials and articles of manufacture comprised of the flame retardant elastomeric materials and non-elastic materials such as polybenzimidazoles, fiberglass, nylons, etc.

ORIGIN OF THE INVENTION

The invention described herein was made in the performance of work undera NASA contract and is subject to the provisions of Section 305 of theNational Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat.435; 42 U.S.C. 2457)

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to novel flame retardant, elastomericcompositions, methods of producing fibers and filaments therefrom and toarticles of manufacture incorporating the elastomeric compositions.

2. Brief Description of the Prior Art

In space exploration, extravehicular activity (EVA) is essential. Suchactivity necessarily requires the use of high strength elastomericmaterials from which to fabricate both garments and carrying bags usedin such activity. The fibers used to form the elastomeric materials musthave good strength, elongation, modulus, and recovery over the extremetemperature and pressure ranges normally encountered in the spaceequipment. Because of the high oxygen atmospheres normally encounteredin space vehicles, the garments, carrying bags, etc. must be flameretardant lest a serious safety hazard be posed. While certain, mainlysynthetic polymeric materials, have the requisite mechanical propertiesand recovery characteristics necessary for use in such environments,they suffer from the infirmity that they are not flame retardant andindeed in many cases are highly flammable.

The prior art, as exemplified by U.S. Pat. Nos. 3,162,609, 3,076,010 and3,134,742, discloses polyurethane compositions showing enhanced flameretardant properties. However, the compositions disclosed in thosepatents are directed towards foamed polymers and not elastomeric typematerial suitable for the production of fibers and filaments. Theproduction of a fire retardant fiber presents special problems becauseof the high surface area of the fiber. Accordingly, attempts to resortto the techniques to render foams and other such structures flameretardant, if applied to fibrous elastomeric materials tends to destroyor seriously impair the physical properties of the fibers therebyrendering them useless for weaving, knitting or other fabric makingtechniques.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a novel,fire retardant composition.

It is another object of the present invention to provide fire retardantelastomeric compositions in which the polymeric backbone hasincorporated therein halogens.

Yet another object of the present invention is to provide a novel classof fire retardant elastomeric polyurethanes produced from halogencontaining polyols.

Still another object of the present invention is to provide novel, flameretardant elastomeric compositions in which a normally flammableelastomer is physically mixed with certain fire retardant additives.

Yet another object of the present invention is to provide flameretardant elastomeric compositions which are totally non-flammable in a70% oxygen atmosphere.

An important object of the present invention is to provide flameretardant elastomeric compositions which have good mechanical andrecovery properties.

Yet another object of the present invention is to provide methods forthe production of fibers or filaments of flame retardant, elastomericcompositions.

These and other objects of the present invention will become apparentfrom the description given herein and the appended claims.

In accordance with the above stated objects, the present invention, inone aspect, provides a flame retardant polyurethane containing anorganic polyisocyanate and a halogen containing polyol, the reactivegroups of the polyol comprising hydroxyl groups, the preferred halogenbeing bromine.

In yet another embodiment of the present invention, the flame retardantcompositions herein are comprised of certain elastomeric syntheticresins and flame retardant additives, the flame retardant additivesbeing either halogenated organic compounds, organic phosphorouscompounds or mixtures of the two.

Another embodiment of the present invention involves a method ofproducing flame retardant, elastomeric filaments or fibers in which theabove described elastomeric composition, if containing a polyurethane ofthe spandex type, is spun into a plurality of fibers which are thencoalesced to a single filament, the coalesced filament beingsubsequently dried. Where the elastomeric polymer is of the fluorocarbontype, a method for producing fire retardant elastomeric filament isprovided which includes extruding the elastomeric composition into afilament or fiber, treating the filament or fiber with a release agentand curing the thus obtained filament at elevated temperatures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The flame retardant compositions of the present invention are basicallyof two general types; polyurethanes which have incorporated in thepolymer backbone, halogen containing polyols, the polyols serving toimpart flame redardancy to the polymer, and conventional elastomericmaterials, which vary in flammability but which are modified by theaddition of certain fire retardant additives to produce compositionswhich are substantially non-flammable.

Polyurethanes which are flexible in nature and therefore suitable forforming fibers have been given the generic term spandex. Generallyspeaking, the term spandex refers to elastomeric fibers in which atleast 85 % of the fiber-forming substance consists of segmentedpolyurethane. The spandex type polyurethanes are referred to assegmented because of the fact that they consist of an alternatearrangement of "soft" segments consisting of either polyester orpolyether blocks and "hard" segments that generally contain aromaticurea and sometimes urethane groups as the rigid components. The rigidsegments are derived from the reaction of the isocyanates with ureaproducing compounds such as amines, water, etc. The production ofpolyurethanes or isocyanate polymers is a well known commercial process,see for instance Kirk-Othmer, The Encylopedia of Chemical Technology,First Supplement, pages 888 et seq, (Interscience, 1957). Briefly, theprocess involves the reaction of an isocyanate and a second compoundwhich contains an active hydrogen group such as a hydroxyl, amino orcarboxy group. The general procedure in the production of polyurethanefibers and the procedure generally employed herein is to treat ahydroxy-terminated polyester or polyether polyol with a polyisocyanate,usually at temperatures between 75° and 125°C to produce what is knownas a prepolymer. Generally speaking, about two moles of thepolyisocyanate are employed for each mole of the polyol to insure thatthe prepolymer is terminated on both ends by an isocyanate group. Theisocyanate terminated prepolymer is then usually dissolved in a suitablesolvent such as, for example, anhydrous dimethylformamide and analiphatic diamine such a hydrazine is added in amounts equivalent to thepolyisocyanate to extend the polymer into the segmented structuredescribed above.

In the preferred embodiment the resulting polymer is linear in characterand it exhibits little or no crosslinking. Thus, the polymer may befabricated by standard thermal processing methods such as extrusion,compression molding, injection molding, etc.; and further, may bedissolved in suitable solvent and be cast (e.g., to form films) or beextruded into fibers.

In preparing the polyurethanes in which the polymer backbone contains ahalogen containing polyol, numerous polyisocyanates can be employed.Nonlimiting examples of useful polyisocyanates include the following:2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate. The phenylenediisocyanates such as 4,4-diphenylmethane diisocyanate, the naphthalenediisocyanates, 1,2,4-benzene triisocyanate, hexamethylene diisocyanate,trimethylene diisocyanate, ethylene diisocyanate, 1,4-cyclohhexylenediisocyanate, 1,3-cyclopentylene diisocyanate and mixtures thereof.Particularly preferred polyisocyanates are 4,4' diphenylmethanediisocyanate and arylene diisocyanates, that is, those in which each ofthe two isocyanate groups is attached directly to an aromatic ring asfor example the toluene diisocyanates.

The other main constituent of the polyurethanes of the present inventionin which halogens are chemically incorporated into the backbone arepolyols containing halogen groups, the reactive groups of the polyolbeing hydroxyl groups. In this group may be mentioned dibromoneopentylgylcol, polyesters of dibromoneopentyl glycol, esters of the productobtained from the reaction of ethylene oxide and tetrobromophthalicanhydride, esters of the product obtained from the reaction of propyleneoxide and tetrobromophthalic anhydride, and esters obtained from thereaction of ethylene oxide, propylene oxide and tetrobromophthalicanhydride. In general, the preferred halogen containing polyols arethose in which the halogen is bromine and particularly preferred arepolyols derived from dibromoneopentyl glycol and tetrobromophthalicanhydride.

Since one of the primary objects of this invention is the development ofa high molecular weight linear, non-cross-linked polymer, it isimportant that all monofunctional and trifunctional impurities beremoved from the dibromoneopentyl glycol prior to reaction. This may beaccomplished, for example, by fractional crystallization from hot water.The monofunctional material, being least soluble, crystallizes fromsolution first. These crystals are then filtered and discarded. Uponfurther cooling of the solution, the desired difunctional materialbegins to crystallize out. These crystals are filtered from solution andrecovered. The remaining solution then contains the highly solubletrifunctional material, which is discarded.

In imparting flame retardancy to the polyurethanes produced herein, thesoft segment of the polymers were modified by forming them from thehalogen containing polyols described above. This can be accomplished inseveral ways. In one method, the halogen containing polyol can bereacted with a difunctional acid such as adipic acid to produce ahydroxy terminated polyester which can in turn be reacted with apolyisocyanate to form an isocyanate terminated polyester prepolymer. Inanother case, the halogen containing glycol can be reacted with thepolyisocyanate to produce a material containing NCO groups which can inturn be reacted with a polyether glycol or a polyester glycol to producethe polyurethane prepolymer. In general, it is desirable that the basepolyol used to produce the prepolymer have a molecular weight of from1500 to 5000. However, polyols having a molecular weight of 1000 can beemployed if they are first reacted with a polyisocyanate such as toluenediisocyanate in a ratio of one mole of polyol to one half mole of thetoluene diisocyanate. This will result in the formation of a base diolhaving a molecular weight of approximately 2000. A particularlydesirable polyester polyol is a polybutylene adipate having a molecularweight of approximately 2000 whereas a desirable polyether polyol ispolytetramethylene ether glycol having a molecular weight ranging fromaround 600 to around 1200.

The above described polyurethane prepolymer having halogen in thepolymer background can be extended to form fire retardant elastomericpolyurethanes having good mechanical properties by reacting them withurea producing compounds such as amines, especially diamines, aparticularly desirable amine being hydrazine.

The reaction of the prepolymers and hydrazine yields of polyurethane ofthe general structure: ##EQU1## wherein R is the soft segment containingthe halogen containing polyol.

The process parameters, including relative proportions of theingredients, used in preparing the halogen containing polyurethanes arethose generally employed in the preparation of spandex typepolyurethanes, the conditions being adjusted according to well knowntechniques to accommodate preparation of a polyester type spandex or apolyether type spandex. Such parameters are set out and described in theabove noted Encylopedia of Chemical Technology and numerous ether wellknown works dealing with the production of polyurethanes.

Elastomeric, flame retardant compositions exhibiting good mechanicalproperties and recovery can also be produced by blending a normallyflammable elastomeric material and certain fire retardant additives.

Nonlimiting examples of elastomeric materials which exhibit some degreeof flammability under certain circumstances but which can be made highlyflame retardant by the addition of specified additives includeconventional polyurethanes of both the polyether and polyester types,chlorinated polymers such as polyvinylchloride, polyvinylidenechloride,fluorinated polymers such as polyvinylfluoride, polyvinylidenefluoride,copolymers of vinyldene fluoride and hexafluoropropylene,polyepichlorohydrins, chlorosulfonated polyethylene, mixtures of theabove, etc. Particularly preferred, because of good mechanicalproperties, are the polyurethanes and the fluoroelastomeres such as areformed from copolymerizing vinylidine fluoride and hexafluoropropylene.Since halogenated polymeric resins contain an inherent degree of flameretardancy due to their halogen content, extremely desirable elastomericformulations can be obtained when a normally, quite flammable elastomersuch as polyurethane is combined with a relatively nonflammableelastomer such as a hologen containing polymer and, in addition, containfire retardant additives are incorporated into the blend.

The fire retardant additives most useful in the composition of thepresent invention fall into two main categories; halogenated compoundsand organic phosphorous containing compounds. As for the halogenatedcompounds, it has been found that the brominated compounds and moreparticularly brominated aromatic compounds are excellent fire retardantadditives and when used in proper proportions, do not destroy themechanical properties of the elastomeric compositions. Nonlimitingexamples of halogen containing additives which can be employed in thecompositions of the present invention includetetrabromoethylene-aniline, hexabromocyclododecane, hexabromobenzene,decabromodiphenyl, decabromopiphenyl oxide, carbon tetrabromide,tetrafluoroethylene, tetrabromoethane, tetrabromobutane, etc. Includedwithin the term halogenated compounds are halogenated polymers.

Nonlimiting examples of the organic phosphorus containing compoundswhich act as useful fire retardant additives in the compositions of thepresent invention include tris-2,3-dibromopropylphosphate,tris-1-bromochloropropylphoshate, tris-beta-chloroethyphosphate,tricresyl phosphate, and the like. Particularly preferred organicphosphorus compounds are tris- 2,3-dibromopropylphosphate,tris-1-bromochloropropylphosphate, tricresylphosphate and mixturesthereof.

Particularly advantageous fire retardancy is achieved by using mixturesof the halogenated, and more particularly the brominated fire retardantadditives and the organic phosphorous containing compounds. Thus, forexample, the use of hexabromobenzene and tris-2,3-dibromopropylphosphatein a polyurethane type composition or the use of decabromodiphenyl andtricresylphosphate in a fluoroelastomeric composition provideselastomeric formulations which exhibit excellent flame retardantproperties together with good mechanical properties and recoverycharacteristics.

In formulating the fire retardant elastomeric compositions of thepresent invention in which a flammable or partially flammable elastomeris admixed with fire retardant additives, the elastomeric material ispresent in the compositions generally in amounts ranging from about 5 toabout 70% by weight. The precise amount of the fire retardant additivesincorporated into the flame retardant compositions will of course varydepending upon the degree of fire retardancy desired, the flammabilitycharacteristics of the elastomer, the maintenance of certain mechanicaland recovery properties and other such parameters. In general, however,the fire retardant additives will be present in amounts ranging fromabout 30 to about 95% by weight.

It is to be noted that in all cases different percentages of theelastomer can be employed, i.e., higher amounts of the elastomerrelative to the fire retardant additive, the result being that the fireretardant properties of the compositions are reduced albeit notcompletely destroyed.

It has been found that when a normally flammable elastomer such aspolyurethane is employed, the amount of fire retardant additive whichmust be incorporated into the composition is generally quite high. Thusfor example when a polyurethane is employed as the elastomer, thecomposition will contain from 3 to 30% of the polyurethane, the balancebeing comprised primarily of fire retardant additives. When relativelynon-flammable elastomer, such as a fluoroelastomer, is employed, theamount of flame retardant additives which must be incorporated toachieve the desired degree of flame retardancy is greatly reduced. Thusin the case where a vinylidine fluoride-hexafluoropropylene copolymersuch as Viton (manufactured by Du Pont) is employed, the amount of theelastomer in the composition will generally vary from about 15 to about65% by weight. It is to be noted that in all cases different percentagesof the elastomer can be employed i.e., higher amounts of the elastomerrelative to the fire retardant additive, the result being that the fireretardant properties of the compositions are reduced albeit notcompletely destroyed.

Other than the above-named fire retardant additives, other fireretardants and other materials such as plasticizers, anti-oxidantscross-linking and curing agents, etc. may be incorporated into thecompositions. It has been found, for example, that the addition ofcertain metal oxides to polyurethane formulations decreased theflammability of the composition. Typically, the fluoroelastomercompositions are cured by means of a diamine (e.g., N,N'-dicinnamylidene-1,6-hexane diamine) and a metal oxide, the preferredmetal oxide for the achievement of flame retardant properties being leadoxide. A particularly effective cure system for the fluoroelastomercompositions is one based on maleimide N-(-4-carboxyphenol) maleimide, aperoxide such as benzoyl or dicumylperoxide, and lead oxide. Thisprovides products with extremely high tensile strength and highelongation that is particularly suitable for making flameproof fiber.Normally, the additional components listed above will not exceed 25% byweight of the composition and more generally will range from about 1 toabout 20% by weight.

When a fluoroelastomer is employed in the flame retardant compositionsof the present invention, it is normally desirable that curing agents beincorporated into the formulation. Thus for example certain metallicoxides such as lead oxide, magnesium oxide, etc., in combination withthe amine type curing agents such as hexamethylene-diaminecarbamate,N-dicinnamylidene-1, 6-hexane diamine, etc., provide excellent curing ofthe compositions. It is to be understood that the curing agentsmentioned above are merely exemplary of curing agents which may beemployed in the elastomeric compositions to obtain the desiredmechanical properties. When a curing agent is employed in thecompositions of the present invention, it will generally be present inamounts ranging from about 25% (wt.) where the percentages apply to thecombined amounts if the curing agent is of the mixed type i.e., metaloxide and amine, or to a single component is such is employed.

Particularly desirable flame retardant elastomeric compositionsemploying a spandex type polyurethane can be produced from a formulationcontaining approximately 15 to 25% of the spandex type polyurethane,approximately 50 to 60% of hexabromobenzene and approxemately 20 to 30%of tris-2,3-dibromopropylphosphate. Likewise, a particularly useful fireretardant fluoroelastomeric composition is obtained from a formulationcontaining 90 to 120 parts of a copolymer of vinylidine fluoride andhexafluorpropylene (Viton), 40 to 60 parts of decabromodiphenol, 10 to20 parts of lead oxide, 3 to 10 parts of tricresylphosphate, and 2 to 7parts of N,N-dicinnamylidene-1,6-hexane diamine.

In preparing fibers or filaments from the elastomeric compositions ofthe present invention, several methods can be employed depending on thenature of the elastomer in the composition. In the case of polyurethanecompositions of the conventional spandex type containing fire retardantadditives or of the type in which halogenated polyols are incorporatedinto the polymeric backbone, a wet spinning technique has been proven tobe most satisfactory. In general, the polyurethane composition isdissolved in a suitable solvent to make a solution containing from about10 to about 20% of the elastomeric composition. Solvents employed incarrying out wet spinning of polyurethanes are well known but in thepresent formulation, dimethylformamide was found to be particularlysatisfactory. Once the polyurethane composition has been dissolved inthe solvent, the solution is fed through a typical spinnerette toproduce a plurality of fibers which are then passed through a suitablewater bath preferably containing in addition to the water, a solvent forthe fiber such as for example the same solvent used to originallydissolve the elastomeric composition. The fibers are taken up from theaqueous bath where excess water and solvent are removed and coalescedinto a single filament, the single filament being dried by passing itslowly on a moving belt system through an elongated drying tunnel keptat between 70° and 90° C. Generally, excess aqueous bath is removed fromthe fibers by passing the fibers through V-shaped pulleys which tend tocoalesce the individual fibers into a single filament and in effectsqueeze out water. Because the modified polyurethanes possess low wetstrength properties, it is necessary that the procedure employed to drythe fibers or filaments be carefully controlled. Thus it was found thatthe technique wherein the fibers were dried on a moving belt passingthrough an oven at the above described temperature gave satisfactoryresults and a fiber exhibiting good mechanical properties.

In producing fibers or filaments of the fluoroelastomer compositions,the technique found most successful was extrusion. In this process, theingredients of the fluoroelastomeric composition are first blended in asuitable fashion such as on a roll mill and granulated into particles,the particles being fed to an extruder. The extruded filaments are thentreated with a release agent such as talcum to prevent fiber-to-fiberadhesion. The fibers are then placed in suitable drying ovens atapproximately 350°-500° F to effect curing.

The fire retardant elastomeric compositions of the present inventionwhen formed into fibers by the techniques described above, can be wovenor knitted into fabric structures exhibiting good mechanical andrecovery properties and having excellent fire retardant characteristics.Moreover, the fire retardant elastomeric fibers can be blended bytechniques such as knitting, weaving, etc., with non-elastic, highstrength materials such as fibrous polybenzimidazoles, nylons containingisophthaloyl chloride fiberglass, etc., to produce articles ofmanufacture having high mechanical strength and exhibiting excellentflame retardant properties. It is also to be pointed out that rigidnon-woven structures can be produced from the flame retardantcompositions of the present invention.

The following non-limiting examples are presented to demonstrate moreclearly the invention. In the examples which follow, as above, allproportions and percentages are by weight unless otherwise indicated.The following general procedures were employed in conducting the testsnoted in following examples:

OXYGEN INDEX TEST

Flammability of the samples was tested by an oxygen-index method(tentative ASTM method, May 14, 1969). In this test, the oxygen index,N, of a material is defined as the percentage concentration of oxygen ina mixture of oxygen and nitrogen at atmospheric pressure that willmaintain equilibrium burning conditions. Physically, this percentage isthe lowest concentration of oxygen that will support sustainedcombustion of the material and is computed according to the formula:##EQU2## where [O₂ ] is the oxygen concentration at equilibrium and [N₂] is the associated nitrogen concentration. Thus, the smaller the valueof N, the more flammable the specimen. In conducting this test, a filmsample of the material 7-15 cm long × 61/2 ± 0.5 mm wide × 0.025 ± 0.01inches thick was placed vertically in the center of a column. The columnwas filled with gases flowing at the rate of 5 cc per second and ignitedby a hydrogen flame. While normal measurements made by this methodinvolve igniting the sample at the top, in the present case, the methodwas modified such that the sample was burned in the selected atmosphereat the bottom of the specimen strip. Two samples were used for each testand the reproducibility of the method was found to be ±1.

TENSILE ELONGATION MEASUREMENTS

Tensile and elongation properties of the formulated elastomercompositions were measured according to ASTM Method 412. The Instrontester was set at a speed of 20 inches/minute and the dumbell was cutwith a die D.

In cases where polymers were synthesized, the following standardprocedures were employed:

A. hydroxyl numbers ASTM D1638

B. acid number ASTM D1638

C. water ASTM D1638

D. free isocyanate ASTM D2572.

In conducting the flammability and mechanical property tests, both castfilms and fibers were employed.

EXAMPLE I

A halogen containing polyester based polyurethane was prepared usingdibromoneopentyl glycol. The purified brominated neopentyl glycol wasreacted with toluene diisocyanates in a 1:2/molar ratio, respectivelyfollowing which the isocyanate-terminated product was reacted with apolybutyl adipate having a molecular weight of approximately 1200. Theresulting polymer possessed the following properties:Wt. % bromine10-11Oxygen index 24-25Ultimate tensile strength, psi 7,000Ultimateelongation, % 500Elasticity GoodRecovery GoodColor Water whiteWt. % softsegment 69.6Wt. % Toluene diisocyanate 12.1Wt. % brominated neopentylglycol 18.3

It is to be noted that the oxygen index of 25 for the polyurethanecontaining the brominated neopentyl glycol compares with an oxygen indexof 19-20 for a normal spandex type polyurethane such as Lycra (productof Du Pont Company). Such an oxygen index i.e., 25, would be sufficientto offer protection in normal air environments, conventional spandextype polyurethanes on the other hand being flammable in normal airenvironments.

EXAMPLE II

The adipic acid ester of a diol obtained by reacting brominated phthalicanhydride and ethylene and propylene oxides was prepared. The resultingadipate had an acid number of 6.83 and a hydroxyl number of 41.4. Thehydroxy-terminated adipate was then reacted with 4,4'-diphenylmethanediisocyanate in a molar ratio of 1:2, respectively to produce anisocyanate-terminated polyadipate prepolymer. This prepolymer was thenextended with hydrazine into a spandex type polyurethane. The resultingmaterial was a strong hard flexible and clear material having an oxygenindex of 30.

EXAMPLE III

The procedure of Example II was followed except azelaic acid wassubstituted for the adipic acid. The material produced was strong, hard,flexible and clear, had greater elasticity than the adipate prepared asper Example II and had an oxygen index of 28.

Examples I-III demonstrate the preparation of spandex type polyurethaneshaving incorporated therein, as part of the polymer backbone, ahalogenated polyol. As observed from the results of the examples, thepolyurethanes produced have oxygen indexes of 25 or greater meaning thatfibers and ultimately fabrics woven or knit therefrom could be usedunder atmospheric conditions without fear of the materials beingflammable. This is to be compared with a conventional type spandexpolyurethane which has an oxygen index of 19-20 and which in normalatmosphere is flammable. It should be noted that by incorporatingcertain of the fire retardant additives noted above into thepolyurethanes prepared in Examples I-III, the fire retardant propertiesof the materials can be enhanced even more.

EXAMPLE IV

A series of elastomeric formulations comprised of a commerciallyavailable spandex type polyurethane (Lycra) and various fire retardantadditives were prepared. Table I shows the compositions of theformulations and the results of the oxygen and flammability testscarried out on the formulations:

                                      TABLE 1                                     __________________________________________________________________________    Sample No.   1     2    3     4    5     6    7     8                         __________________________________________________________________________    % Spandex (Lycra)                                                                          10    10   10    10   20    20   20    20                        % Hexabromobenzene                                                                         45    55   65    75   40    48   56    64                        % Tris-bromochloro-                                                           propylphosphate                                                                            45    35   25    15   40    32   24    16                        Oxygen Index 40-50 45-50                                                                              50-55 55-60                                                                              35-40 40-45                                                                              --    40-45                     Flammability Tests                                                            Rate of Propagation                                                           (inches/second)                                                               Burning 35%                                                                   O.sub.2 -10 psi    SE*             SE    SE   SE                              Burning 100%                                                                  O.sub.2 -6.2 psi   1.66             1.0  1.25 1.42                            Tensile Strength                                                              PSI           373   335  277   310 1157   918  560   727                      Elongation %  600   563  500   125  625   638  600   488                      __________________________________________________________________________    Sample No.    9    10   11    12   13    14   15    16   17                   __________________________________________________________________________    % Spandex (Lycra)                                                                          40    40   40    40   50    50   50    50   5                    % Hexabromobenzene                                                                         30    36   42    48   25    30   35    40   68                   % Tris-bromochloro-                                                           propylphosphate                                                                            30    24   18    12   25    20   15    10   27                   Oxygen Index 35    35-40                                                                              30    30   25-30 25-30                                                                              25-30 30-35                                                                              60-65                Flammability Tests                                                            Rate of Propagation                                                           (inches/second)                                                               Burning 35%                                                                   O.sub.2 -10 psi    0.71                                  SE                   Burning 100%                                                                  O.sub.2 -6.2 psi   1.66                                  1.25                 Tensile Strength                                                              PSI          1750  1905 1657  1726 3090  2625 2994  2956 --                   Elongation %  713   650  563   575  713   675  650   675 --                   __________________________________________________________________________    Control - Spandex Alone                                                                         Oxygen Index                                                                           19                                                                                Tensile PSI                                                                   7100                                                                          Elongation %                                                                  700                                             *Self Extinguishing                                                      

EXAMPLE V

A series of flame retardant formulations containing a commerciallyavailable spandex type polyurethane (Lycra) with various flame retardantadditives were formulated. The results of the oxygen index test, tensilestrength and elongation tests, together with the percentages of theflame retardant additives present are shown in Table 2.

                                      TABLE 2                                     __________________________________________________________________________    Sample                                                                            Fire-Retardant       %     %       Oxygen                                                                             Tensile                                                                             %                           No. Additives      %     Halogen                                                                             Phosphorous                                                                           Index                                                                              Strength                                                                            Elongation                                                                           Comments                                                         (psi)                             __________________________________________________________________________    1   Tris-2, 3-dibromopropyl                                                                      10.66                                                          phosphate            25.9  0.9     25.0 1850  700                             Hexabromobenzene                                                                             16.66                                                      2   Tris-2, 3-dibromopropyl                                                                      25.0                                                           phosphate            39.5  1.3     32.0 1291  660                             Hexabromobenzene                                                                             25.0                                                       3   Tetrabromoethane                                                                             16.33                                                          (Acetylenetetrabromide)                                                                            29.9          22.0 2040  630                             Hexabromobenzene                                                                             16.33                                                      4   Tetrabromoethane                                                                             25                                                             (Acetylenetetrabromide)                                                                            43.7          25.0 2045  670                             Hexabromobenzene                                                                             25                                                         5   Tris-2, 3-dibromopropyl                                                                      25                                                             phosphate            39.2  1.3     28.0 --    --     Poor film                Tetrabromoethane                                                                             25                                                             (Acetylenetetrabromide)                                                   __________________________________________________________________________

EXAMPLE VI

A series of formulations containing a commercially available spandexpolyurethane (Lycra) fire retardant additives and various metal oxideswere prepared. The effect of change of oxygen index caused by additionof the metal oxide is shown in Table 3.

                  TABLE 3                                                         ______________________________________                                                       %                                                              Sample                                                                              %        Organic          %       Oxygen                                No.   Spandex  Halide    Additive                                                                             Additive                                                                              Index                                 ______________________________________                                        1     17       70        Fe.sub.2 O.sub.3                                                                     13      45                                    2     17       70        PbO    13      48                                    3     17       70        Sb.sub.2 O.sub.2                                                                     13      48                                    4     17       70        ZnO    13      38                                    5     17       70        TiO.sub.2                                                                            13      42                                    6     17       70        Cu.sub.2 O                                                                           13      50                                    7     28.6     66.5      MgO     4.9    25                                    8     28.6     66.5      NiO     4.9    38                                    9     17.4     82.6      --      --     50                                    10    28.6     71.4      --      --     45                                    ______________________________________                                    

EXAMPLE VII

A series of formulations prepared from commercially available spandexpolyurethanes (Lycra), various fluorinated elastomeric resins (Viton andFluoral) and hexabromobenzene were prepared. The proportions of thecomponents of the formulations together with the oxygen index values areshown in Table 4. It was noted that Sample 10 would burn slowly in 100%oxygen at 4.2 psi but extinguished in a 70% oxygen/30% nitrogenatmosphere at 6.2 psi. This composition (Sample 10) was also found to betough and resilient.

                                      TABLE 4                                     __________________________________________________________________________    Urethane         Fluorinated Polymer                                                                         Hexabromo-                                                                           Oxygen                                  Sample                                                                            Lycra.sup.1                                                                         Estane.sup.2                                                                         Viton.sup.3                                                                        + Fluorel.sup.4                                                                        benzene                                                                              Index Viton Formulations                No.              Cpd                                                          __________________________________________________________________________    1         22.5          18.75  58.75  65                                      2         15            37.5   65.7   65                                      3         7.5           37.5   55     95                                      4         5.7           45.3   49     95                                      5         7.5           56.25  36.25  75                                      6         15            50     35     50                                      7   7.5                 25     67.5   40                                      8   5.0                 50     45.0   40                                      9   2.5                 75     22.5   50                                      10  4.63                       56.4   80    Viton 35.1, PbO 5.40,                                                         Diak.sup.6 0.40                   11  7.5   1.875         9.375  81.25  50                                      12  5.0   3.75          18.75  72.5   50                                      13  2.5   5.625         28.125 63.75  75                                      14        30                   70      65.sup.5                               15        15                   85      95.sup.5                               __________________________________________________________________________      .sup.1 Trademark for polyurethane produced by E. I. du Pont de Nemours &     Co.                                                                            .sup.2 Trademark for polyurethane produced by B. F. Goodrich Chemical Co      .sup.3 Trademark for fluoroelastomer produced by E. I. du Pont de Nemour     & Co.                                                                          .sup.4 Trademark for fluoroelastomer produced by 3M Company                   .sup.5 30 mil samples                                                         .sup.6 Hexamethylene Diamine Carbamate                                  

EXAMPLE VIII

A series of fire retardant formulations containing various elastomericresins and fire retardant additives were prepared and their flammabilitycharacteristics measured. The compositions of the formulations and theresults of the tests are shown in Table 5. As can be seen from theresults of the table, oxygen index values of 95-100, which are requiredto meet a 100% oxygen specification, can be obtained using a fluorinatedelastomer in combination with hexabromobenzene and a curing agentmixture comprised of lead oxide and Diak. Samples 11-13 depict suchformulations.

                                      TABLE 5                                     __________________________________________________________________________    Sample                                                                            %      %           %                                                      No. Polyurethane                                                                         Fluorinated Polymer                                                                       Hexabrome              Oxygen                              (Lycra)                                                                              (Viton A)   benzene                                                                             Other Additives                                                                           %    Index Comments                  __________________________________________________________________________    1   40.0               42.0  Trisbromachloro- 35-40 Burned 35 O.sub.2                                      propyl phosphate                                                                          18.0       65 N.sub.2                2   30.0               49.0  Trisbromochloro- 40.0  Burned 35 O.sub.2                                      propyl phosphate                                                                          21.0       65 N.sub.2 10 psi                                                             .02"/sec.                 3   5.0    34.7        48.7  Trisbromochloro- 76.0  Burned 70 O.sub.2                                      propyl phosphate                                                                          6.0        30 N.sub.2 10 psi                                                             S.E.                                                   Lead Dioxide (mono)                                                                       5.25       35 O.sub.2 65                                                                 N.sub.2                                                Diak        0.35                                 4   2.5    34.7        50.45 Trisbromochloro- 82.0  --                                                     propyl phosphate                                                                          6.25                                                              Lead Oxide (mono)                                                                         5.25                                                              Diak        0.35                                 5   25.0               52.5  Trisbromochloro- 40-45 S.E. 35 O.sub.2 65                                                            N.sub.2                                                propyl phosphate                                                                          22.5                                 6   20.0               56.0  Trisbromochloro- 45.0  S.E. 35 O.sub.2 65                                                            N.sub.2                                                propyl phosphate                                                                          24.0                                 7   2.5    30.0        62.7  Lead Oxide (Mono)                                                                         4.5  95.0  Slow burning                                           Diak        0.3        100% O.sub.2 S.E. 70                                                          O.sub.2                   8   2.5    35.0        56.9  Lead Oxide (Mono)                                                                         5.25 85.0  S.E. 35 O.sub.2                                        Diak        0.35       65 N.sub.2 10 psi         9   2.5    35.0        54.9  Trisbromochloro-                                                              propyl phosphate                                                                          2.00                                 10  2.5    30.0        56.0  Lead Oxide (Mono)                                                                         4.5  80.0                                                         Diak        0.3                                                               Trisbromochloro-                                                              propyl phosphate                                                                          6.7                                  11         36.0        58.20 Lead Oxide (Mono)                                                                         5.4  87.0  --                                                     Diak        0.4                                  12         30.0        65.2  Lead Oxide (Mono)                                                                         4.5  100   Burns slowly in                                        Diak        0.3        100% O.sub.2 (NASA)       13         25.0        71.0  Lead Oxide (Mono)                                                                         3.75 100   Physically very                                        Diak        0.25       poor                      __________________________________________________________________________

EXAMPLE IX

Three formulations were prepared; in one of the formulations (Sample 1),the elastomeric component was a polyurethane synthesized as per ExampleI. The second formulation (Sample 2) contained a conventionalpolyurethane (Lycra) and the third formulation contained afluoroelastomer (Viton A). The formulations were tested for mechanicalproperties and fire retardancy. The composition of the formulations andthe results of the tests are shown in Table 6.

                                      TABLE 6                                     __________________________________________________________________________    Sample                                                                            Flame Retarding                                                                         % F.R. in                                                                            Poly-                                                                              Oxygen                                                                            Tensile                                                                            %               Propagation                No. Additive  Composition                                                                          urethane                                                                           Index                                                                             Strength                                                                           Elong-                                                                            Pressure                                                                           Composition                                                                          Rate  Comments                                           (psi)                                                                              ation                                                                             (psi)       (in./sec)                  __________________________________________________________________________    1.sup.1                                                                           Hexabromobenzene                                                                        42     40%  45-50                                                                             1300 600 10.0 35% O.sub.2                                                                          0.16  Good                     Tris-1-bromochloro-                                                                     18                                         Elasti-                  propyl phosphate                                     city                 2   Hexabromobenzene                                                                        56     20%  45  880  600 10.0 35% O.sub.2                                                                          0.13  Fair                     Tris-1-bromochloro-                                                                     24                            65% N.sub.2  Elasti-                  propyl phosphate                                     city                 3.sup.2                                                                           Fluorinated polymer                                                                     30                                                                  (Viton A)                                                                     Hexabromobenzene                                                                        45.0        55  940  500 10.0 35% O.sub.2                                                                          Self                                                                                Poor                     Tris-1-bromochloro-                     65% N.sub.2  break                    propyl phosphate                                                                        10.2                      6.2 100% O.sub.2                                                                         0.5   strength                                                                      and                                                                           elasti-                                                                       city                 __________________________________________________________________________     .sup.1 Polyurethane used for this formulation was synthesized as per          Example I.                                                                    .sup.2 This formulation also contains 4.5% lead monoxide and 0.3% Diak.  

Table 7 shows the properties of various elastomeric formulationsprepared in accordance with the present invention as compared with aconventional spandex type polyurethane (Lycra). As can be clearly seen,the formulations prepared in accordance with the present invention showmarkedly enhanced fire retardancy over a conventional spandex typepolyurethane while still retaining adequate mechanical properties.

                                      TABLE 7                                     __________________________________________________________________________    PROPERTIES OF CAST FILM FORMULATIONS                                          Sample    A.sup.(1)                                                                          B.sup.(2)                                                                            C.sup.(3)                                                                            D.sup.(4)                                                                           E.sup.(5)                                                                           F.sup.(6)                            Property                                                                      __________________________________________________________________________    Tensile                                                                       Strength, psi                                                                           --   3530   1047   487   404   1500                                 Elongation, %                                                                           --   641    630    275   500   450                                  Tear Resistance                                                                         --   1.37   0.61   1.77  0.6   --                                   Propagation Rate                                                              at 70% O.sub.2 -                                                              30% N.sub.2, in/sec                                                                     1.33 0.833  --     0.20  0.11  S.E. in                                                                       17/8 in.                             Oxygen Index                                                                            19   25     45     55    100   100                                  __________________________________________________________________________     .sup.(1) Lycra                                                                .sup.(2) Polyurethane prepared as per Example I                               .sup.(3) 20% Lycra, 56% Hexabromobenzene (HBB), 24% Tris-dibromopropyl        phosphate (T-23P)                                                             .sup.(4) 20% of (2), 50% HBB, 24% (T-23P)                                     .sup.(5) 100 parts Viton A (Trademark for fluoroelastomer produced by E.      I. du Pont de Nemours & Co.), 200 parts decabromodiphenyl (DBBP), 30 part     Tricresyl phosphate (TCP)                                                     .sup.(6) 100 parts Viton B (Trademark for fluoroelastomer produced by E.      I. du Pont de Nemours & Co.), 100 parts DBBP, 10 parts TCP                    NOTE: Samples E and F contain in addition a curing system.               

EXAMPLE X

A formulation comprised of 20% Lycra, 56% of hexabromobenzene and 24% oftris-bromochloropropyl phosphate was dissolved in sufficient dimethylformamide to give a 20% by weight solution of the urethane composition.The mixture was ball milled overnight, de-aerated and filtered. Thespinning dope thus prepared was pumped through a spinnerette, the fibersbeing dropped into an aqueous bath to precipitate the fiber andeliminate the dimethyl formamide. The fibers were then passed throughV-shaped rolls which coalesced the fibers and removed the excess water.The filament was then dried by passing it through a tunnel drier at 80°C and recovered on a take-up roll. The spinning conditions employed areshown below:Spinning Head 0.008-inch diameter holes (40)Bath Composition40% DMF, 60% waterBath Temperature 68° FFilament Diameter 0.0012inchSpinning Solution 20% solidsFiller Particle Size 0.5hexabromobenzene

The physical properties of the fibers spun and dried under the aboveconditions were found to be:

    Tensile Strength                                                                              2000-2500 psi                                                 Elongation      475%                                                      

Approximately 5000 ft. of this fiber were spun in deniers ranging from180-210.

EXAMPLE XI

A series of fluoroelastomeric compositions containing Viton B withvarious flame retardant additives and curing agents were formulated andcured. The compositions of the formulations are shown below.

    ______________________________________                                        Sample No.     1         2         3                                                            (Parts by Weight)                                           ______________________________________                                        Viton B        100       100       100                                        Decabromodiphenyl                                                                            100                                                            Hexabromobenzene         100       200                                        PbO            15        15        15                                         Tricresyl phosphate                                                                          10        10        10                                         Diak No. 3     4         4         4                                          ______________________________________                                    

When cured, at 400° F for 16 hrs. melt extruded fibers of the aboveformulations exhibited the following properties:

    Sample No.     1           2        3                                         ______________________________________                                        Tensile Strength, psi                                                                        1300-1500   1500     700                                       Elongation, %  500-600     450      500                                       Oxygen Index   85          80       100                                       ______________________________________                                    

EXAMPLE XII

A series of formulations of various fluoroelastomeric resins incombination with certain flame retardant additives and curing agentswere prepared and extruded into fibers, cured at 400° F for 16 hours andtheir physical and fire retardant properties evaluated. The compositionsof the formulations are shown in Table 8 whereas the results of thephysical and fire retardant property tests are shown in Table 9.

                                      TABLE 8                                     __________________________________________________________________________                 Sample No.                                                       Ingredients  Control                                                                            A   B   C   D   E   F                                       __________________________________________________________________________    Viton A      --   100 --  --  --  --  --                                      Viton B      100  --  80  80  100 100 100                                     Viton LM     --   --  20  20  --  --  --                                      Decabromobiphenyl                                                                          100  100 100 100 100 100 100                                     Zinc Oxide   --   --  --  --  --  10  --                                      Lead Oxide    15   15 15  15   15 --  15                                      Dyphos       --   --  --  --  --  10  --                                      (dibasic lead phosphate)                                                      Tricresylphosphate                                                                         --    10 10  10   10 10  10                                      Antimony Oxychloride                                                                       --   --  --  --  --  --  20                                      Diak No. 3    4    4   4   4  --   4   4                                      Diak No. 4   --   --  --  --   4  --  --                                      __________________________________________________________________________

                  TABLE 9                                                         ______________________________________                                        Fiber    Weight Loss Tensile          Oxygen                                  Formulation                                                                            on Cure     Strength Elongation                                                                            Index                                            (%)         (psi)    (%)                                             ______________________________________                                        Control  2.7         1400     250     85                                      A        6.9         1200     410     85                                      B        6.3         1200     450     85                                      C        5.0         1180     375     85                                      D        1.9         1500     450     85                                      E        7.3         1490     400     85                                      F        6.4         1240     350     85                                      ______________________________________                                    

EXAMPLE XIII

A comparison was made between a standard cure system comprised of DiakNo. 3 and lead oxide and a cure system comprised of maleimide peroxideand lead oxide. As seen in Table 10, formulation 2 using the maleimidesystem provides superior strength and good elongation withoutplasticizer (Tricresyl phosphate). Formulation 2 is particularly usefulin making fibers.

                  TABLE 10                                                        ______________________________________                                        Ingredients        Formulation                                                ______________________________________                                        Viton B            101        102                                             Lead Oxide         100        100                                             N-6-carboxy phenol/maleimide  4                                               Diak No. 3         4                                                          Tricresyl phosphate                                                                              10                                                         Benzoyl Peroxide              4.5                                             Decabromobiphenyl  100        100                                             Tensil Strength-PSI                                                                              1300       2100                                            Elongation percent 500        450                                             Oxygen Index       95-100     95-100                                          ______________________________________                                    

EXAMPLE XIV

A formulation comprised of 100 parts of Viton B, 50 parts ofdecabromodiphenyl, 15 parts of lead oxide, 5 parts of tricresylphosphate and 4 parts of N,N-dicinnamylidene-1, 6-hexane diamine wasblended on an unheated two-roll mill. The formulation was thengranulated to particles approximately 1/16 inch in diameter and fed toan extruder where it was converted into 12 continuous filaments havingdiameters of approximately 13 mils. The extruder was run at 50% ofcapacity, producing approximately one third lb. of fiber per hour(equivalent to 2000 ft/hrs. of fiber). As the fibers exited the die,they were directed individually through guides to vessels where theywere collected in coiled form. The fibers were removed from the vesselsand uncoiled in Pyrex trays into an open, loose pattern. During theuncoiling procedure the fibers were sprinkled liberally with talc toprevent fiber-to-fiber adhesion. The trays were then placed inair-circulating ovens at 400° F for 16 hours to cure the fibers.Following curing the fibers were wound on spools. The fibers thusproduced had physical and fire retardant properties similar to thoseshown in Table 9.

EXAMPLE XV

This example demonstrates the production of fabrics incorporating thefire retardant elastomeric fibers of the present invention with andwithout non-elastic fibrous materials such as fiberglass, certain typesof nylons, particularly those containing isophthaloyl chloride,polybenzimidazoles, etc. Fibers produced from fluoroelastomericcompositions (Viton B) such as those set forth in Table 8 were made intojersey knits from 800 denier fiber. The fabrics exhibited excellenttwo-way stretch.

In another case an 800 denier fiber produced from a fire retardantfluoroelastomeric composition similar to those of Table 8 and containingViton B and a 200 denier continuous filament Nomex (trademark for nylontype material produced by E. I. duPont de Nemours and Company) were madeinto a warp-knit, 36-gauge power net. The resulting fabric exhibitedtwo-way stretch.

A 120-needle jersey consisting of Beta Fiberglas 150 and afluoroelastomeric composition similar to those shown in Table 8 andcontaining Viton as a fluoroelastomer was produced. The Viton fiber,elongated 50-70%, was laid in a weft direction. The fabric exhibitedstretch in the weft direction only.

A power knit fabric was also produced from a thermally stabalizedpolybenzimidazole fiber and a flame retardant fluoroelastomeric fiberproduced from compositions similar to those shown in Table 8.

The fabrics produced from the non-elastic fibers discussed above and theflame retardant elastomeric fibers disclosed herein can be used in manyapplications, particularly in space exploration. For example, thefabrics can be used to produce instrument caps, sleep-restraint gear,space suits, flight suits, fabrics for aircraft, etc.

The compositions disclosed herein find application in any environmentwhere it is desired to use an elastomeric flame resistent materialhaving good mechanical and recovery properties. Thus for example thecompositions can be used to produce open and closed cell foam coatings,tubing, hoses, gaskets and seals.

We claim:
 1. A flame retardant elastomeric composition suitable forforming into fibers comprising a fluorinated elastomer selected from thegroup consisting of polyvinylfluoride, polyvinylidenefluoride, copolymerof vinyldiene fluoride and hexafluoropropylene and mixtures thereof anda flame retardant comprising a brominated organic compound selected fromthe group consisting of hexabromobenzene, decarbromodiphenyl andmixtures thereof, said flame retardant being present in an amountsufficient to render said compositions substantially nonflammable inenvironments containing up to 70% oxygen.
 2. The composition of claim 1wherein said fluorinated elastomer is present in an amount of from about15 to about 65% by weight.
 3. The composition of claim 1 including acuring agent selected from the class consisting of N,N' -dicinnanylidene-1-6-hexane diamine, hexamethylenediamine carbamate andmalemide N-(-4-carboxyphenol) malemide.
 4. The composition of claim 3wherein said curing agent further includes a metal oxide.
 5. Thecomposition of claim 1 wherein said fluorocarbon resin comprises acopolymer of vinylidine fluoride and hexafluoropropylene.